A bone implant typically includes a peg that can be hammered into a pre-drilled hole to secure the implant into a bone. The implant also includes an integrally formed implant body portion for abutment with a mating bone implant.
One possible application for bone implants is knee reconstruction. The peg of one implant is embedded at a suitable attachment site in the tibia and the peg of the other implant is driven into the femur. The facing body portions of each implant serve to replace the original knee joint.
Implants are also used in hip replacements, where the implants provide a ball and socket joint to replace the original functioning of the hip joint.
In some circumstances, one of the pegs may work loose and the associated hole may need to be re-bored and a larger diameter peg used. Alternatively, the implant might simply need replacing, in which case the bone may need to be broken to release the peg. In either case, the surgical procedure is substantial and invasive. Also, bone dimensions and strength characteristics as well as the use of larger diameter pegs may limit the number of implant replacements.
As a result, only a limited number of implant replacements may be viable and installation of an initial implant is generally deferred for as long as possible in the hope the original implant will last a sufficient amount of time. However, considerable pain and discomfort may be experienced if joint replacement is delayed.